WASHINGTON, Aug. 10, 2011 /PRNewswire-USNewswire/ -- After a journey of almost three years, NASA's Mars Exploration Rover Opportunity has reached the Red Planet's Endeavour crater to study rocks never seen before.
(Logo: http://photos.prnewswire.com/prnh/20081007/38461LOGO)
On Aug.

NASA scientists are seeing new evidence that suggests traces of water on Mars are under a thin varnish of iron oxide, or rust, similar to conditions found on desert rocks in California's Mojave Desert.

Mars' Moon Deimos -- outermost of two small moons orbiting the planet Mars. Deimos orbits Mars at a distance of about 23,500 km (about 14,100 mi), completing an orbit once every 1.26 Earth days. The moon's orbit is almost circular and is only slightly tilted relative to the Martian equator.
Deimos is irregular in shape, measuring about 15 km (about 9 mi) along its longest side and about 11 km (about 6.6 mi) along its shortest side. It is the smallest known moon in the solar system.
If...

Mars' Moon Phobos -- in astronomy, innermost moon, or natural satellite, of Mars.
Phobos orbits Mars at a distance of only 9,378 km (5,627 mi), closer to its planet than any other moon in the solar system. In fact, it is so close that the force of Mars's gravity is stronger than the force keeping the moon in its orbit, so the radius of Phobos's orbit is decreasing at the rate of about 1.8 m (about 6 ft) per century.
In 40 million years, Phobos will either break apart into a ring...

A pivoted catch designed to fall into a notch on a ratchet wheel so as to allow movement in only one direction (e.g. on a windlass or in a clock mechanism), or alternatively to move the wheel in one direction.